The Mosin Nagant model M1891/59 carbine was created by shortening M1891/30 rifles to carbine length, with rear sight numbers partially ground off to reflect reduced range. These rifles are almost clones of the M38 except for the ground off M91/30 rear sight. The "1891/59" marking on the receiver suggests the carbines were created in or around 1959. It was initially thought that Bulgaria or some other Soviet satellite country performed the conversions in preparation for a Western invasion that never came. Recent evidence suggests that the M91/59 was indeed produced in Bulgaria from Soviet supplied M91/30s.
The M1891/59 is probably the least well known of the 3 models of carbines and can still be found at a good price.